You will need two things. A pressure regulator and a thermal expansion tank. Household water pressure can have quite a range and be acceptable, but should not exceed 80 psi, but that is still more than necessary. Anywhere from 40 to 60 psi is plenty of pressure. The reason you need a thermal expansion tank is when the water heater does it's job and heats the water, hot water expands. Since water can not be compressed, the expansion has to go somewhere. Before the pressure regulator is installed, this expansion is absorbed by the city water main. However, the PRV has a check valve built into it that prevents this from happening. So the expansion build pressure in the water heater and trips the T/P safety valve to prevent the heater from exploding. Now, the volume of water isn't huge, but it is enough to create a problem. The expansion tank provides a temporary "home" for this expansion. The PRV can be installed anywhere, but in my opinion it should be inside the house where it is easy to access. It is installed in the cold water supply between the PRV and water heater. The high pressure you have is hard on toilet flush valves, dishwasher valves, and clothes washer valves as well, so it should regulate all of the water with the exception of outside hose bibs. The air pressure in the expansion tank should be balanced to equal the PRV setting. Easy to do with a pressure gauge.